[PATCH] bootmenu: Allow to quit it via CTRL+C

[Pali Rohár]

On Saturday 26 December 2020 19:44:23 Heinrich Schuchardt wrote:
> Am 26. Dezember 2020 19:02:25 MEZ schrieb "Pali Rohár" <pali at kernel.org>:
> >When CTRL+C is pressed interrupt bootmenu and jump into U-Boot console.
> >As the last entry in bootmenu is always U-Boot console just choose the
> >last
> >entry when CTRL+C is pressed.
> >
> >It is useful when bootmenu is part of boot process and you want to
> >interrupt boot process by scripts which control U-Boot (serial)
> >console.
> 
> Wouldn't the escape key be a better choice?

I can add also escape key. But has escape key stable ANSI sequence which
is needed to catch? If you tell me which bytes to catch (for escape key)
I will add it.

> On the sandbox CTRL-C makes you quit U-Boot.
> 
> When hitting CTRL-C late on other systems it might interrupt a follow-up command.

I understand your concerns. But all other commands catch also CTRL+C so
I think that bootmenu command should it too.

> --
> 
> The following is not directly related to your patch:
> 
> Is it really a good design that a user cannot be stopped from reaching the console?

Currently "U-Boot console" option is always added to menu list. But
option is doing only one thing: exiting the current U-Boot command and
returning back to the monitor mode.

> I could think of use cases in the context of secure booting where you want to show a menu but you do not want to give access to the command line.

If bootmenu is not started from monitor mode then this "U-Boot console"
command just enter into monitor mode. And I think that you can already
block monitor mode and therefore has ability of this secure boot scheme.

> Best regards
> 
> Heinrich
> 
> >
> >Signed-off-by: Pali Rohár <pali at kernel.org>
> >---
> > cmd/bootmenu.c | 16 +++++++++++++++-
> > 1 file changed, 15 insertions(+), 1 deletion(-)
> >
> >diff --git a/cmd/bootmenu.c b/cmd/bootmenu.c
> >index 1ba7b622e5..9b56bfaa9a 100644
> >--- a/cmd/bootmenu.c
> >+++ b/cmd/bootmenu.c
> >@@ -45,6 +45,7 @@ enum bootmenu_key {
> > 	KEY_UP,
> > 	KEY_DOWN,
> > 	KEY_SELECT,
> >+	KEY_QUIT,
> > };
> > 
> > static char *bootmenu_getoption(unsigned short int n)
> >@@ -109,6 +110,9 @@ static void bootmenu_autoboot_loop(struct
> >bootmenu_data *menu,
> > 			case '\r':
> > 				*key = KEY_SELECT;
> > 				break;
> >+			case 0x3: /* ^C */
> >+				*key = KEY_QUIT;
> >+				break;
> > 			default:
> > 				*key = KEY_NONE;
> > 				break;
> >@@ -187,6 +191,10 @@ static void bootmenu_loop(struct bootmenu_data
> >*menu,
> > 	/* enter key was pressed */
> > 	if (c == '\r')
> > 		*key = KEY_SELECT;
> >+
> >+	/* ^C was pressed */
> >+	if (c == 0x3)
> >+		*key = KEY_QUIT;
> > }
> > 
> > static char *bootmenu_choice_entry(void *data)
> >@@ -222,6 +230,12 @@ static char *bootmenu_choice_entry(void *data)
> > 			for (i = 0; i < menu->active; ++i)
> > 				iter = iter->next;
> > 			return iter->key;
> >+		case KEY_QUIT:
> >+			/* Quit by choosing the last entry - U-Boot console */
> >+			iter = menu->first;
> >+			while (iter->next)
> >+				iter = iter->next;
> >+			return iter->key;
> > 		default:
> > 			break;
> > 		}
> >@@ -389,7 +403,7 @@ static void menu_display_statusline(struct menu *m)
> > 	printf(ANSI_CURSOR_POSITION, menu->count + 5, 1);
> > 	puts(ANSI_CLEAR_LINE);
> > 	printf(ANSI_CURSOR_POSITION, menu->count + 6, 1);
> >-	puts("  Press UP/DOWN to move, ENTER to select");
> >+	puts("  Press UP/DOWN to move, ENTER to select, CTRL+C to quit");
> > 	puts(ANSI_CLEAR_LINE_TO_END);
> > 	printf(ANSI_CURSOR_POSITION, menu->count + 7, 1);
> > 	puts(ANSI_CLEAR_LINE);
>